Expansible fixing plug

ABSTRACT

The invention relates to an expansible fixing plug ( 1 ) which consists of at least two different plastics materials, having a main body ( 2 ) made of the first plastics material, which is at least partly encased by a casing ( 3 ) made of the second plastics material. The main body ( 2 ) has an expansion region ( 5 ), which extends along a longitudinal axis (L) between a sleeve ( 6 ) and an insertion sleeve ( 4 ) forming the rear end of the expansible fixing plug ( 1 ), in which expansion region there are arranged at least two expansion tongues ( 11, 12 ) which are separated from one another by a first slot ( 13 ), the first slot ( 13 ) being at least partly filled in the expansion region ( 5 ) by a casing element ( 21 ) of the casing ( 3 ). In order to obtain an expansible fixing plug ( 1 ) having improved expansion behaviour, it is proposed that on at least one expansion tongue ( 11, 12 ) there be arranged a local weakened position ( 17 ) as predetermined bending point.

The invention relates to an expansible fixing plug having the features of the preamble of claim 1.

FIGS. 5 to 8 of Offenlegungsschrift DE 10 2011 000 537 A1 disclose a generic expansible fixing plug which consists of a plurality of different plastics materials and which is produced in a multi-component injection-moulding process. The expansible fixing plug is used for fixing objects to an anchoring substrate and for that purpose can be inserted into a hole drilled in the anchoring substrate and expanded with an expander element. The expansible fixing plug has the internally located main body made of a first plastics material, shown in FIG. 6 of the Offenlegungsschrift. The main body extends in the longitudinal direction along a longitudinal axis and consists of a tubular insertion sleeve through which a screw, as expander element, can be inserted into an internally located expansion channel extending in the longitudinal direction. The expansion channel extends into an expansion region which adjoins the insertion sleeve and which has four expansion tongues separated from one another by two intersecting slots, which expansion tongues are made of the first plastics material and have a constant cross-section in the longitudinal direction over the expansion region. The expansion region is adjoined in the direction of introduction by a sleeve which consists of two sleeve parts connected by V-shaped resilient connectors which are expansible in the circumferential direction. The main body is at least partly overmoulded with a casing made of a second plastics material. In the expansion region the casing forms expansion elements which are elongated in the longitudinal direction and run parallel to the expansion tongues, which expansion elements, as casing elements of the casing, close the slots between the expansion tongues. The expansion elements are connected to one another in the circumferential direction at their front and rear ends by ring-shaped elements. The ring-shaped elements, like the expansion elements, are parts of the casing and are produced integrally with the expansion elements from the second plastics material. On expansion of the expansible fixing plug, the expansion elements become detached from the expansion tongues of the main body in the expansion region and, like the expansion tongues, are moved radially outwards.

The problem of the invention is to propose an expansible fixing plug that has improved expansion behaviour.

That problem is solved according to the invention by an expansible fixing plug having the features of claim 1. The expansible fixing plug according to the invention, which consists of at least two different plastics materials, comprises a main body made of a first plastics material and a casing made of a second plastics material, the casing at least partly encasing the main body. “Different plastics materials” means plastics materials which differ from one another, for example, in respect of their strength, their elasticity modulus, their chemical composition, their fibre content and/or their colour. The main body has an expansion region which extends in the longitudinal direction along a longitudinal axis and comprises at least two expansion tongues which are separated from one another by a first slot. The length of the first slot accordingly defines the length of the expansion region. As a result of the formation of the first slot, the two expansion tongues can be moved away from one another and expanded in the radial direction, especially by the introduction of an expander element between the expansion tongues. In particular, the two expansion tongues are completely separated from one another by the first slot, but they can also be connected to one another by a thin injection-moulded skin or by resilient elements consisting of the first plastics material, which do not, however, appreciably impede expansion of the expansion tongues but serve to guide an expander element with which the expansion region is expansible. The expansion region extends between a sleeve, which is arranged before the expansion region in the direction of introduction, and an insertion sleeve, which forms the rear end of the expansible fixing plug and through which an expander element can be inserted into the expansion region in the direction of introduction. The “direction of introduction” is the direction in which the expansible fixing plug is introduced as intended into a drilled hole. In particular, there is formed between the expansion tongues an expansion channel for receiving the expander element. The expander element is especially a screw. The first slot is at least partly filled in the expansion region by a casing element formed by the second plastics material of the casing, so that, in comparison with expansible fixing plugs made of only one plastics material with cavities between the expansion tongues, in the expansion region of the expansible fixing plug there is arranged significantly more plastics material which, on expansion, can be displaced radially outwards against the wall of a drilled hole. This has the effect that the expansion tongues of the expansible fixing plug, on expansion in a drilled hole, can be pressed against the wall of the drilled hole with great pressure, with the result that a large frictional force acts between the wall of the drilled hole and the expansible fixing plug and the expansible fixing plug has good hold in the drilled hole.

To improve the expansion behaviour, according to the invention on at least one expansion tongue there is arranged a local weakened position as predetermined bending point. The term “weakened position” is especially to be understood as being generally a local reduction in the cross-sectional surface area of the expansion tongue, with the result that the area moment of inertia of the expansion tongue is locally reduced in such a way that the weakened position forms a bending joint at which the expansion tongue buckles outwards as intended on expansion. As a result, even under a small expansion force acting in the radial direction, as brought about by the introduction of an expander element into the expansion region, the expansion tongue is expansible by outward buckling.

Preferably, the weakened position is arranged in the longitudinal direction in a central region of the expansion tongue, that central region being the central third of the expansion tongue, relative to the length of the expansion tongue, between the sleeve and the insertion sleeve. The arrangement of the weakened position in the central region of the expansion tongue results in uniform expansion of the expansion tongue in a hollow building material, that is to say when the expansion region is not completely surrounded by the wall of a drilled hole and the sleeve is drawn towards the insertion sleeve by a screw inserted into the expansion region as expander element and the expansible fixing plug is thereby shortened and axially compressed.

The weakened position can consist of one part or a plurality of parts. It is preferred that at least a part of the weakened position is arranged on the inside in the radial direction. For the case where an expansion channel is arranged between the expansion tongues, “on the inside” means the side facing the expansion channel. Preferably, the part of the weakened position arranged on the inside of the expansion tongue is at least partly, especially completely, filled by the second plastics material, which especially forms a part of the casing element. The expansion tongue with the internally located weakened position filled by the second plastics material acts in a drilled hole in a solid building material in which the expansion region is surrounded by the drilled hole and the expansion tongue buckles outwards only to a very small extent on expansion, substantially in a similar way to an expansion tongue that has no weakened position and expands uniformly over its length. On the other hand, the weakened position filled with the second plastics material can act as a predetermined bending point in a hollow building material, because the casing element made of the second plastics material becomes detached from the expansion tongue and accordingly does not impede outward buckling.

Alternatively or in combination, at least a part of the weakened position can be arranged on the outside of the expansion tongue in the radial direction. In particular, the weakened position is arranged on the inside and on the outside of the expansion tongue in the radial direction, with the result that the bending joint can be configured as desired, without the need to make the inner or outer weakened position larger than is necessary for slots or openings, as are customary for expansible fixing plugs.

Preferably, at least a part of the weakened position is slot-like or wedge-like in shape. Alternatively or in combination, at least a part of the weakened position is preferably circular-segment-shaped. By the provision of a slot-shaped, wedge-shaped or circular-segment-shaped weakened position, the buckling or expansion behaviour can be controlled by simple geometric shaping of the expansion tongue.

Preferably, a second slot, especially running in the longitudinal direction of the expansible fixing plug, is arranged in the sleeve. The second slot is inclined with respect to the first slot. That means that a plane in which the first slot lies intersects, at an angle, a plane in which the second slot lies. In particular, the two slots, i.e. the two planes in which the slots lie, are orthogonal with respect to one another.

Preferably, on introduction of an expander element the expansion region of an expansible fixing plug according to the invention is expanded substantially in a first radial expansion direction, while the sleeve is expanded in a second radial expansion direction different therefrom. “Substantially” means here that on introduction of the expander element the expansion region or the sleeve widens to a greater extent in a preferred expansion direction than in other directions. However, this does not exclude the expansion region and/or the sleeve from also widening in other directions or from widening in circumference as a whole. In particular, the first slot is for that purpose configured in such a way that it does not extend into the sleeve. In particular, the two radial expansion directions of the expansion region and the sleeve are substantially orthogonal with respect to one another, with “substantially” here meaning that a deviation of +/−10° is possible.

An expansible fixing plug having regions with different expansion directions has the advantage that the fixing plug has not only a preferred expansion direction but at least two expansion directions. The expansion forces arising during expansion of the expansion region and the sleeve are accordingly introduced into the anchoring substrate and distributed in different radial directions, with the result that relatively large forces can be introduced from the expansible fixing plug into the anchoring substrate.

The invention is explained in greater detail below with reference to two exemplary embodiments, wherein

FIG. 1 is a side view of a first expansible fixing plug according to the invention;

FIG. 2 is a perspective side view of the main body of the first expansible fixing plug;

FIG. 3 is an axial section through the first expansible fixing plug along the axis III-III;

FIG. 4 is a section through the first expansible fixing plug along the axis IV-IV;

FIG. 5 is a section through the first expansible fixing plug along the axis V-V; and

FIG. 6 is a perspective side view of the main body of a second expansible fixing plug according to the invention.

FIGS. 1 to 5 show a first expansible fixing plug 1 according to the invention which, for fixing an object (not shown), can be introduced into a drilled hole (not shown) and expanded with an expander element, especially a screw (not shown). The expansible fixing plug 1 consists of a main body 2 made of a first plastics material and a casing 3 made of a second plastics material different from the first plastics material. In the exemplary embodiment, the first plastics material is a polyamide, while the second plastics material is a polypropylene. In FIG. 2 the main body 2 is shown without the casing 3 and consists of an insertion sleeve 4, which is arranged at the rear of the main body 2 in the direction of introduction E, an expansion region 5 which adjoins the insertion sleeve 4 in the direction of introduction E, and a sleeve 6 arranged at the front of the main body 2. The direction of introduction E is the direction in which the expansible fixing plug 1 is introduced as intended into a drilled hole. In the exemplary embodiment, the insertion sleeve 4, through which an expander element can be introduced as intended into the expansible fixing plug 1, is in the form of a short hollow cylinder which extends along the longitudinal axis L and on the outer side of which there are arranged four rear anti-rotation ribs 26. At the rear end of the insertion sleeve 4 there is arranged a circumferential collar 7 which forms the rear end of the main body 2 and of the expansible fixing plug 1 and prevents the expansible fixing plug 1 from being introducible too deeply into a drilled hole. The sleeve 6 arranged at the front of the main body 2 consists of two half-shell-like sleeve parts 8, 9 which are connected to one another by three V-shaped resilient connectors 10, so that, on introduction of an expander element, the sleeve 6 is expansible in the radial direction, with the connectors 10 being stretched in the radial direction. Between the sleeve 6 and the insertion sleeve 4, the expansion region 5 extends along the longitudinal axis L.

The expansion region 5 has two expansion tongues 11, 12 which are formed by a first slot 13 which extends in the longitudinal direction of the expansible fixing plug 1 and in a first radial direction r₁ and passes completely through the main body 2 in the expansion region 5. In FIGS. 1 and 2 the first radial direction r₁ runs perpendicular to the plane of the drawing. The axial length of the first slot 13 defines the axial length of the expansion tongues 11, 12 and accordingly the length of the expansion region 5. Because the two expansion tongues 11, 12 are completely separated from one another by the first slot 13, on introduction of an expander element the expansion tongues 11, 12 can be moved away from one another and expanded in a first expansion direction s₁. The first expansion direction s₁ is orthogonal with respect to a plane in which the first slot 13 is located. In order that the expansion tongues 11, 12 can be expanded by even a small expansion force produced on insertion of an expander element into the expansion region 5 and acting in the first expansion direction s₁, the expansion tongues 11, 12 have local weakened positions 17 which act as predetermined bending points. The weakened positions 17 are arranged in the expansion region 5 approximately centrally in the longitudinal direction on the expansion tongues 11, 12 between the sleeve 6 and the insertion sleeve 4 and each consist of two parts: an inner part 17 a, which is arranged on the inside of the expansion tongues 11, 12 in the radial direction and which is in the form of a conically sloping, circular-segment-shaped hollow, and an outer part 17 b, which is arranged on the outside of the expansion tongues 11, 12 in the radial direction and which has a slot-like or wedge-like shape. On expansion, the two expansion tongues 11, 12 buckle outwards at the weakened positions 17 and are moved away from one another in the first expansion direction s₁ and orthogonally with respect to the first radial direction r₁ or to a plane in which the first slot 13 is located.

As shown in FIGS. 3 and 4, the first slot 13, together with a second slot 14, forms in the expansion region 5 an expansion channel 15 for receiving an expander element (not shown). The second slot 14 extends in the longitudinal direction of the expansible fixing plug 1 and in a second radial direction r₂ which is orthogonal with respect to the first radial direction r₁ and parallel to the first expansion direction s₁. As a result of the two slots 13, 14, which intersect one another and are inclined with respect to one another, the expansion channel 15 is cross-shaped and has, in the region in which the two slots 13, 14 intersect, a central screw channel 16 of circular cross-section. The screw channel 16 serves to guide a screw (not shown) which is screwed into the expansion channel 15 as expander element and extends into the sleeve 6. The second slot 14 extends in the second radial direction r₂ only to an extent such that it does not pass through the main body 2 in the expansion region 5. The second slot 14 weakens the expansion tongues 11, 12 locally so that there is formed on the expansion tongues 11, 12 a kind of hinge 28 a which runs parallel to the longitudinal axis L and has the effect that the expansion tongues 11, 12, which are almost semi-circular in cross-section, can adapt to an uneven wall of a drilled hole (not shown).

While the first slot 13 is arranged exclusively in the expansion region 5 and does not extend into the sleeve 6, and accordingly defines the length of the expansion region 5, the second slot 14 extends into the sleeve 6 and, like the screw channel 16, runs almost as far as to the front end of the expansible fixing plug 1, as can be seen in FIG. 3. The second slot 14 likewise does not pass through the two sleeve parts 8, 9 in the radial direction, with the result that in the two sleeve parts 8, 9 there are likewise formed hinges 28 b in such a way that the two sleeve parts 8, 9 can themselves likewise be deformed along an axis running parallel to the longitudinal axis L. In addition, the second slot 14 divides the sleeve 6 in the interior of the sleeve 6, with the result that the second slot 14 defines a second expansion direction s₂ running orthogonally with respect to the slot 14, in which direction the sleeve 6 is substantially expanded on introduction of an expander element. As a result of the resilient connectors 10, the sleeve 6 will also become wider in the second radial direction r₂ but not to the extent possible in the second expansion directions s₂ as a result of the second slot 14. Since the slots 13, 14 are orthogonal with respect to one another, on introduction of an expander element the expansion region 5 expands substantially in the first radial expansion direction s₁, while the sleeve 6 expands substantially in the second radial expansion direction s₂ which is different therefrom and is orthogonal with respect to the first expansion direction s₁.

The sleeve 6 is partly encased by a casing body 18 of the casing 3. In order to prevent the casing 3 from being displaced relative to the sleeve 6 on expansion of the expansible fixing plug 1, ribs 19 and elongate blocks 20 are arranged on the outside of the sleeve 6 of the main body 2. Four ribs 19 are formed on each of the two sleeve parts 8, 9 in the form of radially outwardly located parts of a circular ring which run in the circumferential direction and are spaced apart from one another in the longitudinal direction, which parts are surrounded and enclosed by the casing body 18 in such a way that the ribs 19 hold the casing body 18 in fixed axial position on the sleeve 6. The distances between adjacent ribs 19 correspond to the axial extent of the ribs 19. The two blocks 20 are parallelepipedal in shape and run in the longitudinal direction of the expansible fixing plug 1. A block 20 is arranged on each rear part of the sleeve 6, the blocks 20 extending into the expansion region 5. The blocks 20 are surrounded in the circumferential direction and in the longitudinal direction by the casing 3 which they pass through in the radial direction. The blocks 20 prevent movement of the casing body 18 on the sleeve 6 in the circumferential direction.

FIG. 6 shows an alternative main body 2′ in which the ribs 19′ slope wedge-like in the direction of introduction E, with the result that limited movement of the casing body 18 on the sleeve 6 is possible. As a result of the wedge-like slope, movement of the casing body 18 in a direction opposite to the direction of introduction E results in additional expansion of the casing body 18, which improves the holding power of the expansible fixing plug 1 in a drilled hole.

On the casing body 18 there are arranged two casing elements 21 in the form of wing elements 22 which, starting from the casing body 18, extend cantilever-like into the expansion region 5 in a direction opposite to the direction of introduction E and substantially in the longitudinal direction L (see FIGS. 1, 3 and 4). The two wing elements 22 are arranged on radially opposite sides of the expansion region 5 of the expansible fixing plug 1 and, apart from being connected via the casing body 18, are not connected to one another. The connection to the casing body 18 is integral, rigid and resistant to bending. The two wing elements 22 lie in openings 24 which are formed by groove-like, parallelepipedal recesses 23, the first slot 13 and the inner parts 17 a of the weakened positions 17 in the expansion region 5. The recesses 23 run on the outside of the expansible fixing plug 1 in the longitudinal direction thereof and are relatively small in relation to the size of the expansion tongues 11, 12 and weaken the expansion tongues 11, 12 only to a negligible extent. The two wing elements 22 are accordingly also arranged between the two expansion tongues 11, 12 and extend over the entire length of the expansion region 5. The wing elements 22, which are made of the second plastics material, completely fill the first slot 13, from an outer face 25 of the expansible fixing plug 1 to the screw channel 16, and also the openings 24 and the inner parts 17 a of the weakened position 17. The internally located second slot 14, however, is not filled with the second plastics material of the casing 3. In order that the insertion of an expander element into the expansion region 5 is not impeded by the wing elements 22, at their rear ends 29 that face the insertion sleeve 4 the wing elements 22 slope on the inside with respect to the longitudinal axis L of the expansible fixing plug 1. The wing elements 22 are of cantilever-like construction such that they expand even under very small expansion forces, especially when the expander element presses only against the rear ends 29 of the wing elements 22. The design of the wing elements 22 as cantilevers has the advantage that the expansion forces act on the rear ends 29 of the wing elements 22 with a large lever arm towards the site of connection with the casing body 18, so that even a small expansion force is sufficient to press the rear ends 29 of the wing elements 22 radially outwards despite the bending-resistant connection to the casing body 18. In the unexpanded state of the expansible fixing plug 1, that is to say before the insertion of an expander element into the expansion channel 15, the wing elements 22 project beyond the main body 2 in the radial direction in the expansion region 5. This becomes clear in the sectional view in FIG. 3: the expansion region 5 has a constant external diameter D_(S) over its length, while the two wing elements 23 in the rear region widen wedge-like in a direction opposite to the direction of introduction E so that in the region of their rear ends 29 they have a larger diameter D_(F) than the expansion region 5. The wing elements 23, together with the rear anti-rotation ribs 26 and two front anti-rotation ribs 27, which are formed on the outside of the expansion tongues 11, 12 and extend, in some places discontinuously, over the length of the expansion region 5, counteract co-rotation of the expansible fixing plug 1 in a drilled hole when an expander element is screwed into the expansion channel 15.

Because the openings 24 in the expansion region 5 and regions between the sleeve parts 8, 9 of the sleeve 6 are filled with the second plastics material, when the expansible fixing plug 1 is expanded in a drilled hole surrounding the expansible fixing plug 1 it is possible for a relatively large amount of material to be pressed against the wall of the drilled hole, the use of different plastics materials enabling the parts of the expansible fixing plug 1 to remain movable with respect to one another and readily deformable for expansion. As a result, the expansible fixing plug 1 can have a very compact and short shape, with the ratio between the length L from the front end of the sleeve 6 to the rear end of the expansion region 5 and the diameter Ds of the expansion region 5 being approximately 5.

LIST OF REFERENCE SYMBOLS Expansible Fixing Plug

-   1 expansible fixing plug -   2, 2′ main body -   3 casing -   4 insertion sleeve -   5 expansion region -   6 sleeve -   7 collar -   8 first sleeve part -   9 second sleeve part -   10 connector -   11 first expansion tongue -   12 second expansion tongue -   13 first slot -   14 second slot -   15 expansion channel -   16 screw channel -   17 weakened position -   17 a inner part of the weakened position 17 -   17 b outer part of the weakened position 17 -   18 casing body -   19, 19′ rib -   20 block -   21 casing element -   22 wing element -   23 recess -   24 opening -   25 outer face of the expansion region 5 -   26 rear anti-rotation rib -   27 front anti-rotation rib -   28 a hinge of an expansion tongue 11, 12 -   28 b hinge of a sleeve part 8, 9 -   29 rear end of a wing element 22 -   D_(F) external diameter of the wing elements 22 -   D_(S) external diameter of the expansion region 5 -   E direction of introduction -   L longitudinal axis -   r₁ first radial direction -   r₂ second radial direction -   s₁ first expansion direction -   s₂ second expansion direction 

1. An expansible fixing plug which consists of at least two different plastics materials, having a main body made of the first plastics material, which is at least partly encased by a casing made of the second plastics material, wherein the main body has an expansion region, which extends along a longitudinal axis (L) between a sleeve and an insertion sleeve forming the rear end of the expansible fixing plug, in which expansion region there are arranged at least two expansion tongues which are separated from one another by a first slot, the first slot being at least partly filled in the expansion region by a casing element of the casing, wherein on at least one expansion tongue there is arranged a local weakened position as predetermined bending point.
 2. The expansible fixing plug according to claim 1, wherein the weakened position is arranged in the longitudinal direction in a central third of the expansion tongues.
 3. The expansible fixing plug according to claim 1, wherein at least a part of the weakened position is arranged on the inside of the expansion tongue in the radial direction.
 4. The expansible fixing plug according to claim 3, wherein the part of the weakened position arranged radially on the inside of the expansion tongue is at least partly, especially completely, filled by the second plastics material.
 5. The expansible fixing plug according to claim 1, wherein at least a part of the weakened position is arranged on the outside of the expansion tongue in the radial direction.
 6. The expansible fixing plug according to claim 1, wherein at least a part of the weakened position is slot-shaped or wedge-shaped.
 7. The expansible fixing plug according to claim 1, wherein at least a part of the weakened position is circular-segment-shaped.
 8. The expansible fixing plug according to claim 1, wherein in the sleeve there is arranged a second slot which is inclined with respect to the first slot.
 9. The expansible fixing plug according to claim 1, wherein on introduction of an expander element, the expansion region expands substantially in a first radial expansion direction (s₁), while the sleeve expands substantially in a second radial expansion direction (s₂) different therefrom. 